1. Field of the Invention
The present invention relates to a method for forming a headrest adapted for use on an automotive seat, and more particularly to the method of this kind wherein the headrest is formed by injecting a liquid foaming base material into the interior of a preformed three-dimensional trim cover assembly having a predetermined headrest outer shape and then subjecting both liquid foaming base material and trim cover assembly to foaming integrally together.
2. Description of Prior Art
According to a typical known foaming process for producing a headrest, a three-dimensional trim cover assembly of a predetermined headrest shape is firstly provided by sewing together required separate cover sections, with an opening defined therein, then a generally U-shaped headrest frame having a pair of headrest stay portions is inserted through the opening into the interior of the trim cover assembly, and thereafter, a liquid base foaming material is injected and cured in the trim cover assembly, so as to produce a foamed resultant headrest with the pair of headrest stay portions projecting therefrom.
This foaming process has encountered the problem that the liquid base foaming material is leaked through the opening to the outside of trim cover assembly, leaving an objectionable spot thereon. Conventionally, in an attempt to prevent the leakage of liquid base foaming material, typical solution is for example found in the Japanese Granted Patent Pub. No. 6-45149 and Japanese Laid-Open Patent Pub. No. 7-31759, wherein a pair of extensions are formed in the portion of trim cover assembly corresponding to that opening such as to extend inwardly from the opening into the trim cover assembly, and a flattened tubular film piece is fitted between the pair of extensions, so that an injection nozzle can be inserted through the flattened tubular piece into the interior of trim cover assembly, and, during the foaming process, the liquid base foaming material being injected from the nozzle is prevented by those two extensions and film from the opening in question.
However, such conventional method requires cutting of an externally exposed part of the film which projects outwards from the opening, subsequent to the foaming process, thus resulting in a troublesome labor on the part of worker and also in the high likelihood of a cut, tear or undesired damage being given to the trim cover assembly when the worker cuts off the film.